Hydrogen capped fluorocarbon polyethers



United States Patent 3,342,875 HYDROGEN CAPPED FLUOROCARBON POLYETHERS Stanley Selman, Wilmington, and Wilburn Suber Smith, Jr., New Castle, Del., assignors to E. I. du Pont de Nemours and Company, Wilmington, Del., a corporation of Delaware No Drawing. Filed Mar. 26, 1962, Ser. No. 182,618 9 Claims. (Cl. 260-615) where n is the number of repeating epoxide units formed from N molecules of the epoxide. Additionally, flu0rocarbon polyethers of slightly diflering structures may also be prepared by polymerization of these epoxides in the presence of an acid fluoride, as illustrated by the following equations:

(III) C FRICOF where R, is a fluorine'or a trifluoromethyl radical and n and m are numbers of repeating epoxide units in the polyether chains derived from N and M molecules of the epoxide.The polymerization illustrated is broadly applicable to fluorocarbon acid fluorides which can be monobasic or dibasic.

The fluorocarbon polyethers illustrated in the foregoing equations can be prepared by a number of methods. Thus, hexafluoropropylene epoxide and tetrafluoroethylene epoXide are polymerized in accordance with Equations I and II using bulk polymerization techniques and an active charcoal catalyst. Hexafl-uoropropylene epoxide can also be polymerized employing a monovalent metal fluoride or a quaternary ammonium or phosphonium salt as the catalyst in organic polar solvents, such as the dimethyl ether of ethylene glycol, the dimethyl ether of diethylene glycol, dioxane, acetonitrile, propionitrile and 3,342,875 Patented Sept. 19, 1967 benzonitrile. The preferred classes of organic polar solvents are aliphatic polyethers having from 4 to 10 carbon atoms and hydrocarbon nitriles having from 2 to 10 carbon atoms. However, other organic polar solvents, such as nitroethane, tetrahydrofuran, dimethylsulfoxide, acetone and ethyl acetate, may also be employed as reaction diluents. Tetrafluoroethylene epoxide may also be polym erizecl using quaternary ammonium and phosphonium salts as catalysts in halogenated solvents such as methylene chloride, chloroform, and 1,1,2,2-tetrafluoro-3-chloropropane. The reactions described in Equations III and IV are carried out by employing the aforementioned ionic catalysts and reaction diluents in the presence of a fluorocarbon acid fluoride. As is apparent from the equation, both monoand diacid fluorides can be employed. Suitable acid fluorides include carbonyl fluoride, trifluoroacetyl fluoride, .perfluoropropionyl fluoride, oxalyl fluoride, diacid fluorides of perfluoromalonic acid, perfluorosuccinic acid, perfluoroglutaric acid and perfluoroadipic acid, perfluoroheptanoyl fluoride and similar acid fluorides. In addition to the completely fluorinated acid fluorides, there may also be reacted with the fluorocarbon epoxide substantially perfluorinated acid fluorides having the general formula XR' COF in which R"', is a perfluoroalkylene radical, such as perfluoromethylene, perfluoroethylene or perfluorotrimethylene, and X is a hydrogen or a different halogen.

It is an object of the present invention to improve the chemical stability of the described fluorocarbon polyethers by chemically modifying the carbonyl fluoride endgroup of the fluorocarbon polyether.

The hydrogen modified fluorocarbon ethers of the present invention have the general formulas where R is a fluorine or a trifluoromethyl radical, R, is a perfluoroalkylene radical having preferably from one to five carbon atoms, X is a radical selected from the class consisting of hydrogen and halogen, R", is a perfluoroalkylene radical having at least two carbon atoms, and, preferably from two to ten carbon atoms, and n and m are integers, representing numbers of repeating fluorocarbon epoXide units in the polymer, which can vary from 0 to 50.

The hydrogen capped fluorocarbon ethers of the present invention are obtained by one of two reactions. Thus, they may be obtained by the pyrolysis of a hydrogen con- 'taining derivative of the ether, such as the fluorocarbon ether acid or the ammonium salt of the fluorocarbon ether acid, or they may be obtained by the reaction of a monovalent metal salt, preferably an alkali metal salt, of a fluorocarbon polyether acid of the type illustrated in reactions I through IV hereinabove with water or an organic solvent which contains an active hydrogen. Although water can be used in this reaction, it is not preferred since high temperatures are required to form the hydrogen capped fluorocarbon ether. In general, the organic solvents are hydroxyl group containing hydrocarbon solvents such as alcohols, acids and phenols. In a preferred embodiment, the active hydrogen containing solvent is employed as an aqueous solution. A preferred 3 4 class of these reagents are aliphatic monoand polyhydric dimethyl ether of diethylene glycoland 0.1 g. of cesium alcohols. Examples of such reagents are methanol, ethfluoride. Hexafluoropropylene epoxide was then charged anol, butanol, ethylene glycol, diethylene glycol, cycloto the reaction vessel unt l a pressure of 5 p.s.1. was athexanol, propylene glycol, trimethylene gycol and glycertained. The vessel was agitated at a temperature of 25 to 01. However, other active hydrogen containing solvents 5 30 C. for a perlod of one hour. The pressure wasmalnmay also be used. These include acetic acid, propionic tained at the indicated level by the further addition of acid, phenol, etc. the epoxide. The resulting product be1ng insoluble in the The formation of the hydrogen modified fluorocarbon diluent was separated and 57 g. of a fluorocarbon polypolyethers of the present invention as applied to homot r Was tamed having the formula polymers of the epoxides may be illustrated by the fol- CF CF CF CF lowing equations: 2- n a)- lROH CFzRt-CF2O(CFRCFaO)uCFRrH ROM 00, where R and n have the same meaning as above, M is a where n varied from 4 to 6. The fluorocarbon polyether monovalent metal and ROH is an active hydrogen conhaving the formula taining solvent. The foregoing reaction scheme is also CF CF CF CF CF COP applicable to adducts of perfluorocarbon acid fluorides 3) 2 and fluorocarbon epoxides. These are formed using or- 15 obtained by carrying out the foregolng reaction in the ganic polar solvents and ionic catalysts described above. P e f Carb nyl fluoride. If the reaction 18 carrled By employing mild conditions and excess quantities of the out In the Pfeseflee 0f oxalyl fiuorlde, fluorocarbon acid fluoride, polymerization of the epoxide is substanp ly th r havmg the formula tially suppressed. These compounds, therefore, have the COF (CF3)CF EO CF2 CF(cP-a);}nO CF2 formulas and "r[- r ]2 is obtained. i hi h R R' R" d X h h Same meaning as Into a dry pressure vessel stirred with a magnetic stirrer above. was added 160 mg. of tetraethyl ammonium cyanide and The hydrolysis of the acid fluoride of the fluorocarbon 3 of a halogenated Solver!t havlng the formula ether occurs on contact of the ether with water. The CHFfiCFfhCHZCI formation of the monovalent metal salt is similarly ob- 40 o tained by contacting the acid with an aqueous solution of The flask 9 cooled to and -1 g- O tr fluoroh metal h d id h Salt, furth r can be acetyl fluorlde and 155 g. of tetrafluoroethylene epoxlde rectly formed by the reaction of the fluorocarbon ether were added Slowly Y a 5 hour period. The temperacid fluoride with an aqueous solution of the metal hythe feaehol'l lmXtufe Was m ln ln d at i 35 i5 C. a nd the pressure of the mixture ranged The reaction of the fluorocarbon ether acid salt with from 44 R' lhlhahy to T E h h at the end of the active hydrogen containing reagent can be carried out the e h The p 1n P ssur lndlcates a nearly over a i temperature range f 0 to C, if quantitative conversion of the reagents. Fractional distili However, a fa t and complete reaction is lation resulted in a fluorocarbon ether and fluorocarbon tained if temperatures in the range of 100 to 300 C. are polyether havlhg the general formula employed. The hydrogen capped fluorocarbon ether is ;1: c0

formed when the two reagents are combined. In a preferred technique, the two reagents are admixed and the resulting mixture is distilled. The hydrogen capped fluorocarbon ether distills out of the mixture. For higher molecular weight fluorocarbon ethers that cannot be readily distilled, other suitable methods will be apparent to those skilled in the art. The quantity of solvent is not critical, but is preferably employed in excess of the stoichiometric where n varied from 0 to 6. Similar products, but of higher molecular weight, are obtained in the absence of the trifluoroacetyl fluoride. In the presence of a diacid fluoride a fluorocarbon polyether having two carbonyl fluoride end groups is obtained.

The present invention is further illustrated by the following examples.

quantity required. If desired, the formation of the acid EXAMPLE I salt may be carried out in situ by admixing the acid, the Into a distillation flask containing 150 ml. of water active hydrogen containing compound and the metal hyand 150 ml. of ethylene glycol was added 44.15 g. of a droxide simultaneously, i.e., combining steps two and polytetrafluoroethylene epoxide ether having the formula three in the foregoing reaction scheme. It is also feasible to combine all three steps and thus use the fluorocarbon G5 F (CF2 CF2 O}4CF2COF ether formed by the polymerization of the epoxide or The mixture was made alkaline and distilled. Over the the reaction of the epoxide with an acid fluoride. The range of to C. water distilled from the mixture. pyrolysis of the hydrogen containing derivative of the In the range of 140 to C. a mixture of water and fluorocarbon ether is carried out at temperatures of 115 22 ml. of a fluorocarbon distillate was collected. After to 450 C., in accordance with techniques well established 70 separation, drying and distillation 27.5 g. of omega-hydroin the art for the pyrolysis of fluorocarbon compounds. fluorocarbon l th h i th f l The preparation of the fluorocarbon ethers employed as starting materials in the process of the present inven- F%CFZ CFZ O}4CF2H tion is illustrated by the following specific examples: Into B.P. 128 to 129 C., RP. 73 to 72 C., sp. gr. 1.6 a 50 ml. glass reaction flask was charged 2 ml. of the 75 was obtained.

Into a distillation flask containing 400 ml. of ethylene glycol was added 465 g. of a hydrolyzed polyether of hexafluoropropylene epoxide having the formula and 400 ml. of 2.5 molar KOH. The alkaline solution was slowly distilled at 115 to 200 C. over a three hour period. The water and 234 ml. of fluorocarbon distillate were collected and separated. After drying over Na SO the fluorocarbon was distilled to yield 400 g. (93% yield) of pure hydroperfluoropropylene epoxide polyether having the formula F[CF(CF )CF P-]- CFHCF B.P. +151 to 152 C. Analysis by gas chromatography indicated a single compound. Analysis by IR showed the characteristic C-H bands at 3.4 and 6.8 1 along with the broad CF absorption from 7.4 to 9.5,u. and in addition bands at 10.1, 11.1, 12.3 and 133 Analysis.Calcd.: C, 21.37; H, 0.16; F, 70.70. Found: C, 21.57; H, 0.26; F, 72.38.

EXAMPLE HI Into a reaction flask cooled to 60 C. was placed 46.4 g. of 2-perfluoromethoxy-perfluoropropionyl fluoride and 32 g. of aqueous potassium hydroxide (concentration 50 wt. percent). The excess water in the mixture was then evaporated by applying a vacuum for a period of 24 hours and maintaining the salt at a temperature of 60 C. under an aspirator for a period of 12 hours. The resulting wet salt was heated to 230 C. and theproducts distilling out of the heated mixture were condensed. There was obtained 17.6 g. of product which on analysis by gas chromatography contained 86.9% of CF OCFH-CF EXAMPLE IV Into a thin platinum tube was placed 2.6 g. of the ammonium salt of 2-perfluoropropoxy perfluoropropionic acid. The tube was heated to 225 C. and 200 atmospheres were applied to the tube. The tube was opened and the contents were distilled under vacuum into a nitrogen cooled graduate cylinder, and resulted in about 1.1 ml. of a clear liquid. Nuclear magnetic resonance analysis of this sample showed it to be Elemental analysis gave the following results. Calculated for C F OH: C=2l%; F-=73.1%. Found: C=20.8%, 20.7%; F=69.8%.

EXAMPLE V Into a Carius tube was placed 0.2 g. of Z-perfluoropropoxy perfluoropropionic acid. The tube was sealed and heated at 380 C. for two hours. The resulting product was found to have the formula hydrogen capped fluorocarbon polyether having the formula 6 EXAMPLE V11 To a flask containing 50 g. of'a viscous polytetrafluoroethylene epoxide oil, having the formula rtcr -cr oa ce cor where n varied from 1 to 30, was added 200 ml. of water and 200 ml. of ethylene glycol. The reaction mixture was made alkaline with potassium hydroxide and was heated for 8 hours from -135 C. The mixture was cooled and the lower fluorocarbon layer separated to give 32 g. of a hydrogen capped fluorocarbon ether having the general formula F{-CF CF O') CF H, where n varied from 1 to 30. The product was identified by vapor phase chromatography and infrared, analysis. Distillation gave 4 g. of product boiling from 91-125 C., 14.6 g. boiling from l33 C. at 21 mm., 12.2 g. boiling from 133 C. at 21 mm. to 198 C. at 2/10 mm. and 1.0 g. of high boiling oil. The infrared spectra of all fractions showed complete removal of carbonyl absorption and the presence of CH absorption.

EXAMPLE VIII A 26.8 g. sample of a copolymer containing 81 mole percent tetrafluoroethylene epoxide and 19 mole percent hexafluoropropylene epoxide was stirred with 200 ml. of water and 200 ml. of ethylene glycol. Neutralization of the mixture with aqueous potassium hydroxide gave an average molecular weight of 4000 for the polymer and a range of 5 to 40 for the degree of polymeriza tion. The alkaline mixture was stirred for 12 hours at 135 C., cooled and the lower fluorocarbon layer separated. The product Weighed 20.1 g. and melted at 25- -27 C. Distillation gave the following fractions:

Fraction Weight, Boiling Point Freezing g. Polnt, C.

3. 1 115 O./0.2 mm. to 70 C./0.2 mm 2. 5 C./0.2 mm. to 200 C./0.2 mm. 3. 9 202 C./0.2 mm. to 258 C./0.2 mm 19. 3 to 22 1. 4 260 C./0.2 mm. to 264 C./0.2 mm. 30 to 32. 6 5. 8 Of higher boiling residue The infrared absorption spectra for these materials indicated their complete conversion to hydrogen capped material.

EXAMPLE IX Using the procedure of Example I, a fluorocarbon ether having the formula C F -EO'CF(CF )-OOF] is converted into the hydrogen capped ether having the formula 3 2.

EXAMPLE X Using the procedure of Example I, a fluorocarbon ether having the formula C F {-OCF COF) is converted into the hydrogen capped fluorocarbon ether having the formula C F {-O CF H) EXAMPLE XI Using the procedure of Example I, a fluorocarbon ether having the formula is converted into the hydrogen capped fluorocarbon ether having the formula The foregoing examples have illustrated the formation of the hydrogen modified fluorocarbon ethers of the present invention. As can be seen from the examples, the reaction leading to the formation of these fluorocarbon ethers is readily accomplished by admixing the polyether and the active hydrogen containing solvent and distilling the mixture. Various modifications of the reaction techniques illustrated by the examples will be apparent to 7 those skilled in the art and are included in the scope of the invention.

The hydrogen modified fluorocarbon ethers of the present invention are chemically inert, and stable over a wide range of temperatures. They, furthermore, possess an extremely wide liquid state temperature range. In view of these properties, the hydrogen modified fluorocarbon ethers of the present invention have outstanding utility as lubricants, dielectric media and heat transfer media. The ethers, furthermore, are useful solvents and plasticizers for halogenated compounds and resins.

What is claimed is:

1. A hydrogen modified fluorocarbon ether having formulas of the class consisting of where R, is a radical selected from the class consisting of the fluorine and the trifluoromethyl radical, R is a perfluoroalkylene radical of one to five carbon atoms, X is a radical selected from the class consisting of hydrogen and halogen, R"; is a perfluoroalkylene radical of at least two carbon atoms and n and m are integers from 0 to 50 inclusive.

2. A hydrogen modified fluorocarbon ether having the formula where R", is a perfluoroalkylene radical having from two to ten carbon atoms and n and m are integers from 0 to 50 inclusive.

3. The hydrogen modified fluorocarbon ether of claim 2 wherein R", is the tetrafluoroethylene radical.

4. A hydrogen modified fluorocarbon ether having the is a perfluoroalkylene radical of one to five carbon atoms,

X is a halo-gen and n an integer from 0 to 50 inclusive.

5. A hydrogen modified fluorocarbon ether having the 5 formula XR -O- [CF (CF CF O]- CF (CF H, where R' is a perfluoroalkylene radical of one to five carbon atoms, X is a halogen and n an integer from 0 to 50 inclusive.

6. The hydrogen modified fluorocarbon ether of claim 5 wherein X is fluorine.

7. The hydrogen modified fluorocarbon ether of claim 6 wherein R f is a difluoromethylene group.

8. The hydrogen modified fluorocarbon ether of claim 6 wherein R; is a tetrafluoroethylene group.

9. The hydrogen modified fluorocarbon ether of claim 6 wherein R; is a hexafluoropropylene group.

References Cited FOREIGN PATENTS 5/1959 Canada. 1/1947 Great Britain.

OTHER REFERENCES La Zerte et al., Jour. Amer. Chem. Soc., vol. 75 (1953), pages 4525-4528.

35 LEON ZITVER, Primary Examiner.

B. HELFIN, H. T. MARS, Assistant Examiners.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3,342,875 September 19, 1967 Stanley Selman et a1.

It is certified that error appears in the above identified patent. and that said Letters Patent are hereby corrected as shown below:

Columnl, line 46', "FC should read CF Column 2, line 35, should read CF Signed and sealed this 24th day of March 1970.

(SEAL) Attest:

i WILLIAM SCHUYLER, JR.

Edward M. Fletcher, Jr.

Cmiimissioner of Patents Attesting Officer 

1. A HYDROGEN MODIFIED FLUOROCARBON ETHER HAVING FORMULAS OF THE CLASS CONSISTING OF 